<form id='myupload' action='http://localhost:8080/uploadSign' method='post' enctype='multipart/form-data'>
  <div class="demo">
    <div class="btn">
      <span>添加附件</span>
      <input id="fileupload" type="file" name="file1"></div>
    <div class="progress">
      <span class="bar"></span>
      <span class="percent">0%</span></div>
    <!-- 显示已上传的文件名 -->
    <div class="files"></div>
    <!-- 显示已上传的图片-->
    <div class="showimg"></div>
  </div>
  <input type="submit" onclick="gosubmit2()" /></form>
<script src="https://cdn.bootcss.com/jquery/1.6.4/jquery.js"></script>
<script type="text/javascript" src="https://cdn.bootcss.com/jquery.form/4.1.0/jquery.form.min.js"></script>
<script type="text/javascript">var bar = $('.bar'); //进度条
var percent = $('.percent'); //获取上传百分比
var showimg = $('.showimg'); //显示图片的div
var progress = $('.progress'); //显示进度的div
var files = $('.files'); //文件上传控件的input元素
var btn = $('.btn span'); //按钮文本
function gosubmit2() {
  $("#myupload").ajaxSubmit({
    dataType: 'json',
    //返回数据类型
    beforeSend: function() {
      showimg.empty();
      progress.show();
      var percentVal = '0%';
      bar.width(percentVal);
      percent.html(percentVal);
      btn.html('上传中..');
    },
    //更新进度条事件处理代码
    uploadProgress: function(event, position, total, percentComplete) {
      var percentVal = percentComplete + '%';
      bar.width(percentVal);
      percent.html(percentVal);
    },
    success: function(data) { //图片上传成功时
      //获取服务器端返回的文件数据
      alert(data.name + "," + data.pic + "," + data.size);
    },
    error: function(xhr) {
      btn.html(上传失败);
      bar.width('0');
      files.html(xhr.responseText);
    }
  });
}</script>